US nanotechnologists are developing what they think could be the ultimate non-stick surface.

The needles are just a couple of millionths of a metre apart

It is covered with nano-scale needles that enable a liquid, for example, to slip straight off it.

One application could be non-stick submarines, which would glide through the water with much less resistance and require less force and fuel to propel them.

"If you think about submarines in a marine environment, the defence department will be very excited to hear about this," CJ Kim, an engineer at the University of California at Los Angeles, told BBC World Service's Discovery programme.